EIGRP Packets

EIGRP when running in a routed environment utilizes five types of packets. A Hello, Update, Query, Reply and Acknowledgement (ACK) packet.

Hello Packets

Pretty much used for neighbor discovery. Multicasts with ACK # of 0.

Update

Update packets contain route change information. They are send to affected routers. Updates routers that the particular route has used to converge. Sent as multicasts when a route becomes passive. Syncs by unicasting during startup. Sent reliably.

Query

Performed in route computation when no FS is found. Sent to neighbors asking if they have a route to destination. Usually multicast but can be send as unicast. Sent reliably.